An air-cooled fin-type heat exchanger is very well known. Heat exchangers are used for changing the temperature of various working fluids, such as an engine coolant, an engine lubricating oil, an air conditioning refrigerant, and an automatic transmission fluid, for example. The heat exchanger typically includes a plurality of spaced apart fluid conduits or tubes connected between an inlet tank and an outlet tank, and a plurality of heat exchanging fins disposed between adjacent conduits. Air is directed across the fins of the heat exchanger by a cooling fan or a motion of a vehicle, for example. As the air flows across the fins, heat in a fluid flowing through the tubes is conducted through the walls of the tubes, into the fins, and transferred into the air.
One of the primary goals in heat exchanger design is to achieve the highest possible thermal efficiency. Thermal efficiency is measured by dividing the amount of heat that is transferred by the heat exchanger under a given set of conditions (amount of airflow, temperature difference between the air and fluid, and the like) by the theoretical maximum possible heat transfer under those conditions. Thus, an increase in the rate of heat transfer results in a higher thermal efficiency.
Typically, to improve thermal efficiency the airflow must be improved and/or a pressure drop through the heat exchanger must be reduced. Improved heat exchanger performance can be accomplished by forming the fins and/or louvers on the fins at a predetermined angle in a manner also well known in the art. Pressure drop is associated with the change in airflow direction caused by the louvered fins. A higher air pressure drop can result in a lower heat transfer rate. Various types of fin and louver designs have been disclosed in the prior art with the object of increasing the heat exchanger efficiency by making improvements in the fins, louvers, and airflow pattern.
Examples of these prior art fin and louver designs include an addition of fin rows in order to increase the amount of air encountered by the heat exchanger. Other designs include louvers formed at an angle to the fin wall, rather than square to the fin wall. Further, the prior art discloses heat exchangers with multiple changes of airflow direction. Air flows through the louvers until a middle transition piece or turnaround rib is reached. The air then changes direction and flows through exit louvers to exit the heat exchanger. Fin design continues to play an important role in increasing heat exchanger efficiency.
It would be desirable to produce a fin for a heat exchanger whereby a pressure drop associated therewith is minimized and an airflow through the heat exchanger is maximized.